problem resolved
rm a.txt
init a.txt
update a.txt
Revert "update a.txt"

This reverts commit 8f1551c739bfa84b0f6beac772c500b8bb95d21a.
update a.txt to 3
resolve conflict
update a.txt
update a to 100
update a to 111
update a.txt
Merge branch 'master' of github.com:josephjsf/myAndroidProj